Human glomerulonephritis (GN) and its glomerulosclerotic (GS) sequela are a major cause of renal failure necessitating expensive dialysis and transplantation therapy. Better understanding of the immune pathogenesis and therapeutic manipulation of the underlying molecular mechanisms of sclerosis would stall buildup of extracellular matrix (ECM) and loss of nephron units in GS. Two areas of this problem will be studied from a molecular perspective: 1) the reactive epitopes/V-gene interactions and possible abnormalities of alpha3 (IV) collagen chains in anti-glomerular basement membrane (GBN) antibody (Ab) GN and Alport syndrome as well as assessment of protein-protein interactions with the alpha-chains; 2) the role of ECM proteinases and their inhibitors in excess accumulation of ECM in GS. The genomic DNA for the carboxyl terminal NCI domain of alpha3(lV) collagen, a major anti-GBM Ab Ag, was cloned with evidence of alternatively spliced mRNAs which vary relative to one another during kidney development. The carboxyl terminal variations predicted by the alternatively spliced mRNAs may be control mechanisms and could help to explain Ag variations among patients as well as structural abnormalities in GBM of patients with Alport syndrome in whom alpha3 (IV) Ag may be missing. A combination of synthetic peptides, biochemical fractions, and expressed recombinant fragments, including unique deduced peptides from the spliced mRNAs of alpha3(IV) and their reactive Abs, will help define anti-GBM Ab epitopes and their variations in normal and Alport GBM. The epitope knowledge will be related to the V-gene composition of the autoantibody as an avenue to immunospecific treatment. Inhibitors (PAI 1, TIMPs) of ECM proteinases may impair ECM degradation during sclerosis. The role of the proteinases (u-PA, transin) and their inhibitors, as well as often associated coagulation proteins, will be sought in manipulative experimental studies (including mice transgenic for PAI 1 and transin) and in immunocytochemical and molecular studies in human renal biopsies. These studies will document molecular and enzymatic abnormalities in GN and GS and set the stage for evaluation of molecular therapy.